Frequency of hepatitis B virus 'a' determinant variants in unselected Spanish chronic carriers

Hepatitis B escape mutants in Scottish blood donors

Hepatitis B virus (HBV) remains as the viral infection with the highest risk of transmission by transfusion. This risk is associated with window period donations, occult HBV infection (OBI) and the emergence of escape mutants, which render blood donations false negative for hepatitis B surface antigen (HBsAg) serological testing. A retrospective study was conducted to gain insights into the molecular epidemiology of HBV escape mutants in Scottish blood donors. The criterion for selection was HBV positivity either by serology or nucleic acid testing (NAT). HBsAg detection was compared across several commercial immunoassays. The full length S gene from plasma samples was PCR amplified, cloned and expressed in HepG2 cells. Eight samples showed HBsAg discordant results, while 5 OBI samples were found. Four escape mutants, containing missense mutations in the S gene, are described here. These mutations impaired HBsAg detection both from HBV infected plasma samples and from recombinant proteins derived from its infected donors. Phylogenetic analysis showed that most of the mutants were clustered in the genotype D and were closely related to strains from Asia and the Middle East. We report here a proline substitution, outside the major hydrophilic region, that impaired HBsAg detection in vivo and in vitro, warning about the risk for the emergence of vaccine escape mutants with mutations outside the major neutralisation site.

HBsAg variants: diagnostic-escape and diagnostic dilemma

A wide variety of commercial assays is available for the detection of hepatitis B surface antigen (HBsAg). Clearly, the sensitivity of an assay to detect a variant is dependent on the anti-HBs usage. Thus, it is not surprising that there are examples of variants that cannot be detected by all assays. Data from Europe, Asia and Africa about HBsAg variants which are not recognized by either monoclonal or polyclonal antibodies specific for wild-type group 'a' determinant, but positive by DNA polymerase chain reaction (PCR) in chronic patients and from vaccinated children are increasing. This would impose a challenge for public health issues of hepatitis B virus. In this review we tried to summarize the discrepancies between results of HBsAg assays and to explain some rationales for these inconsistencies.

Comprehensive analysis of the prevalence of hepatitis B virus escape mutations in the major hydrophilic region of surface antigen

Escape mutations in the major hydrophilic region (MHR) of hepatitis B surface antigen (HBsAg) are reported widely worldwide; these mutations lead to diagnostic problems, emergence of vaccine-escape mutants, and hepatitis B immunoglobulin (HBIG) therapy failure. However, the prevalence of these mutations in different genotypes remains to be studied systematically. In the current study, 11,221 non-redundant hepatitis B virus (HBV) sequences of 8 genotypes (from A to H), obtained from the National Center for Biotechnology Information (NCBI), were analyzed to determine the prevalence of HBsAg escape mutations that were previously described. Eight important mutations associated with diagnostic failure, P120T, T126S, Q129H, G130N, S143L, D144A, and G145A/R, were prevalent in one or more genotypes, with the frequency of no less than 1%. With regard to escape variants that evade vaccine or immunoglobulin therapy, mutations were located mainly at positions 120, 126, 129, 130, 133, 134, 137, 140, 143, 144, and 145. The majority of such mutations showed genotypic heterogeneity, indicating the different distribution of the escape mutations. Most of the escape mutations clustered in the "a" determinant, indicating that this region was more likely to be affected by immune selection or antiviral therapy than other regions. Understanding the prevalence and heterogeneity of escape mutations could provide useful guidance for the improvement of diagnostic assays, design of new vaccines, and prevention of failure of HBIG therapy.

Molecular epidemiological study of hepatitis B virus in blood donors from five Chinese blood centers

Although the genetic variability of hepatitis B virus (HBV) in HBV-infected patients has been extensively studied, reports on genotypes, subtypes and mutations in the S region of HBV strains from Chinese blood donors are limited. In this study, 245 blood samples from HBsAg-positive blood donors were collected from five geographically diverse blood centers in China. The S region of HBV was amplified, and the HBV genotype and subtype were determined. The amino acid sequences of the S region were aligned, and mutations related to the failure of immunization and HBsAg detection were determined. Of the 245 samples, 228 (93 %) were genotyped successfully. We found that genotypes B, C, D and A accounted for 58.8 %, 21.9 %, 6.6 % and 3.95 % of the isolates, respectively. The distribution of HBV antigen subtypes was as follows: adw (67.6 %), adr (23.3 %) and ayw (8.7 %). Mutations were present in 39 (17.1 %) of 228 samples in the major hydrophilic region (MHR) of the S region. This study demonstrated that HBV genotype/subtype B/adw was the most frequent strain circulating in HBV-infected Chinese blood donors, followed by C/adr. The occurrence of MHR mutants in HBV-infected blood donors and the potential failure to detect some of them in collected units poses a threat to transfusion safety.

Reactivation of hepatitis B virus with mutated hepatitis B surface antigen in a liver transplant recipient receiving a graft from an antibody to hepatitis B surface antigen- and antibody to hepatitis B core antigen-positive donor

BACKGROUND

Fresh-frozen plasma (FFP) may contain antibodies to hepatitis B surface antigen (HBsAg, anti-HBs). These anti-HBs may lead to a misinterpretation of the actual hepatitis B immune status. Furthermore, they may not only confer protection against hepatitis B virus (HBV), but may also favor the selection of HBsAg mutants.

CASE REPORT

We report a case of de novo HBV infection in a HBV-naïve recipient with alcoholic liver disease, who received a liver from a donor with antibodies to hepatitis B core antigen (HBcAg, anti-HBc) and anti-HBs.

RESULTS

A lookback investigation revealed the following: 1) Due to anti-HBs passively acquired through FFP, the recipient was considered immune to HBV and did not receive anti-HBV prophylaxis. 2) Within 1 year after transplantation he developed hepatitis B in absence of any elevated liver enzymes after the anti-HBs by FFP declined. 3) Despite an infection with HBV-containing wild-type HBcAg, the patient did not seroconvert to anti-HBc positivity. 4) The replicating HBV encoded two HBsAg mutations, first sQ129R and 4 months later sP127S. They map to the highly conserved “α” determinant of the HBsAg loop.

CONCLUSION

1) Passive transfer of anti-HBs from FFP led to an erroneous pretransplant diagnosis of HBV immunity when the patient was in fact HBV-naïve. 2) HBsAg mutations might have been selected in escape from donor's actively produced anti-HBs and the recipient's anti-HBs by FFP might have favored this selection. 3) It is doubtful whether hepatitis B immunoglobulin could have prevented the reactivation. 4) Antiviral prophylaxis would have been crucial.

Hepatitis B surface gene 145 mutant as a minor population in hepatitis B virus carriers

BACKGROUND

Hepatitis B virus (HBV) can have mutations that include the a determinant, which causes breakthrough infection. In particular, a single mutation at amino acid 145 of the surface protein (G145) is frequently reported in the failure of prophylactic treatment. The aim of this study was to evaluate the frequency of the a determinant mutants, especially the G145 variant, in Japan, where universal vaccination has not been adopted.

METHODS

The present study was a retrospective study. The study cohorts were defined as follows: group 1, children with failure to prevent mother-to-child transmission despite immunoprophylaxis (n = 18, male/female = 8/10, age 1-14 years; median 6 years); group 2, HBV carriers who had not received vaccination or hepatitis B immunoglobulin (n = 107, male/female = 107, age 1-52 years; median 16 years). To detect the G145R and G145A mutants in patients, we designed 3 probes for real-time PCR. We also performed direct sequencing and cloning of PCR products.

RESULTS

By mutant-specific real-time PCR, one subject (5.6%) was positive for the G145R mutant in group 1, while the G145 mutant was undetectable in group 2. The a determinant mutants were detected in one (5.6%) of the group 1 subjects and 10 (9.3%) of the group 2 subjects using direct sequencing, but direct sequencing did not reveal the G145 mutant as a predominant strain in the two groups. However, the subject who was positive according to the mutant-specific real-time PCR in group 1 had overlapped peaks at nt 587 in the electropherogram. In group 2, 11 patients had overlapped peaks at nt 587 in the electropherogram. Cloning of PCR products allowed detection of the G145R mutant as a minor strain in 7 (group 1: 1 subject, group 2: 6 subjects) of 12 subjects who had overlapped peaks at nt 587 in the electropherogram.

CONCLUSIONS

The frequency of the a determinant mutants was not high in Japan. However, the G145R mutant was often present as a minor population in children and adults. HBV carriers might have the a determinant mutants as a minor form.

Hepatitis B virus S gene escape mutants

Hepatitis B virus (HBV) can be classified into nine immunological subtypes or eight genotypes. The most prevalent genotypes in Asia are genotypes B and C. HBV is transmitted parenteraly and can produce either asymptomatic or symptomatic disease. Although the consequences of acute hepatitis B can be severe, serious sequelae are associated with chronic infections. HBV seroprevalence ranges from intermediate (2%-7%) to high (≥8%) levels in Asia. Several strategies for the control and prevention of HBV infection have been found to be efficacious. They include vaccination and the administration of HBIG, interferon-a and nucleoside/nucleotide analogues. However, these procedures also apply selective pressures on HBV in infected individuals leading to the generation and accumulation of mutations in the S gene. Most of these mutations occur in the major hydrophilic region (MHR) of the S gene. These mutations create public health concerns as they can be responsible for reactivation of hepatitis B and occult hepatitis B infection. The inability to detect occult infections means that these individuals may become blood donors. This suggests that new strategies for donor evaluation and selection may need to be developed to protect the blood supply.

High levels of serum hepatitis B virus DNA in patients with 'anti-HBc alone': role of HBsAg mutants

It remains unclear how the detection of hepatitis B core antibody (anti-HBc) in the absence of hepatitis B surface antigen (HBsAg) and antibody (anti-HBs) should be interpreted and whether all patients with this pattern need to be tested for hepatitis B virus (HBV)-DNA. This study aimed at reassessing the significance of 'anti-HBc alone' in unselected sera referred to the clinical laboratory and determining whether significant HBV viraemia can be found in this setting. Of the 6431 patients tested for HBsAg, total anti-HBc and anti-HBs in a Paris hospital over a 1-year period, 362 (5.6%) had 'anti-HBc alone' (24.8% of anti-HBc-positive patients). Only 11 of the 362 sera (3.0%) were found to be false positive. One patient was in the resolving phase of acute hepatitis B. HBV-DNA was detected in 10 of 362 (2.8%) patients, using a commercial standardized assay (threshold: 350 IU/mL). Viral loads exceeded 10(4) copies/mL in 6 of 10 patients. Mutations in the HBsAg immunodominant region were identified in seven of the viraemic patients. HBsAg was detected in only two cases when retested by one of the latest, multivalent assays. Neither human immunodeficiency virus nor hepatitis C virus serostatus distinguished between patients with and without HBV-DNA. In conclusion, 'anti-HBc alone' should be considered a risk marker for a so-called 'false occult' HBV infection with significant viraemia. Indeed, results in this hospital population indicate that a small proportion of patients with 'anti-HBc alone' have high viral loads, revealing the occurrence of infection with HBV mutants that escape detection even by multivalent HBsAg assays.

Hepatitis B genotypes/subgenotypes and MHR variants among Moroccan chronic carriers

OBJECTIVES

The aim of this study was to determine the prevalence of Hepatitis B Virus (HBV) genotypes, subgenotypes, HBV surface antigen (HBsAg) subtypes and naturally occurring mutations in Major Hydrophilic region (MHR) of HBsAg among Moroccan patients with chronic HBV infection.

METHODS

The study included 200 patients chronically infected with HBV. The HBV genotypes, subgenotypes, HBsAg subtypes and MHR variants were determined by direct sequencing of the HBV surface (S) gene and phylogenetic analysis.

RESULTS

The S gene was successfully amplified in 134 patients. The mean age was 40.6 ± 12.2 years. Genotype D was predominant (90%, 120/134) and genotype A was less frequent (10%, 14/134). Genotype D strains belonged to subgenotypes D7 (70.8%, 85/120), D1 (25.8%, 31/120) and D2 (0.9%, 1/120). Three strains (2.5%) could not be classified in any subgenotype of genotype D. All genotype A strains belonged to subgenotype A2. HBsAg subtypes found were ayw2 (82.1%, 110/134), adw2 (10.4%, 14/134), ayw3 (3%, 4/134) and ayw4 (3%, 4/134). The global prevalence of MHR variants was 15% (20/134) with substitution P120T/S the most frequent (3.7%, 5/134). The occurrence of MHR variants was significantly associated with advancing age (>40 years) (p = 0.003) and independent of sex, HBeAg status, viral load, genotype, subgenotype and HBsAg subtype.

CONCLUSIONS

This study provides the first description of predominance of HBV subgenotype D7/subtype ayw2 among Moroccan HBV chronic carriers. It also showed a significant prevalence of naturally occurring MHR variants in Morocco.

Prevalence of hepatitis B virus MHR mutations and their correlation with genotypes and antiviral therapy in chronically infected patients in Serbia

Understanding the prevalence and diversity of HBsAg variants in a population is fundamental to assay design and planning vaccination programs. It has been shown that mutations within the S gene, caused by selection or natural variation, can lead to false-negative results in assays for HBsAg, or have clinical implications, such as evading anti-HBV immunoglobulin therapy or vaccine-induced immunity. The region of HBsAg where most of these mutations occur is known as the major hydrophilic region (MHR). The aim of this study was to determine the prevalence and mutational patterns of MHR mutations in patients with chronic hepatitis B, and their correlation with patient characteristics, viral factors and antiviral therapy. The study comprised 164 plasma samples from patients with chronic hepatitis B, of which, 34.8% were on long-term lamivudine monotherapy. Direct sequencing of part of the S/pol gene was used for identification of HBsAg mutations, HBV genotypes, subgenotypes and HBsAg subtypes. The overall frequency of MHR mutations was 22.6%, but it varied significantly between untreated and treated patients (16.8% vs. 33.3%). The most frequent substitution was at position 120 (9.1%) whereas the most common vaccine-escape position, 145, was affected in 1.8% of isolates. The presence of MHR mutations was correlated with genotype D, subgenotype D3, and ayw2/ayw3 HBsAg subtypes and to older age (>40 years). It is concluded that natural viral variability present in a geographical region, duration of infection, and antiviral therapy are among the major factors associated with the occurrence of MHR mutations.

Monitoring of hepatitis B virus surface antigen escape mutations and concomitantly nucleos(t)ide analog resistance mutations in Turkish patients with chronic hepatitis B

BACKGROUND

The hepatitis B virus (HBV) polymerase gene completely overlaps with the envelope gene. In the present study we aimed to monitor the prevalence and pattern of the typical mutations for hepatitis B surface antigen (HBsAg) escape, and concomitantly nucleos(t)ide analog (NUC) resistance mutations, in Turkish patients undergoing different antiviral therapies and in treatment-naïve patients with chronic hepatitis B (CHB).

METHODS

The investigation was undertaken between March 2007 and August 2009 and involved a total of 142 patients under NUC therapy (88 males; mean age 42 years (range 13-68); hepatitis B e antigen (HBeAg) negativity in 94 patients; HBV DNA median log 4.3 log(10) IU/ml (range 2.0->6.0); alanine aminotransferase (ALT) median level 76.1 IU/ml (range 12-1082)) and 185 treatment-naïve CHB patients (120 males; mean age 39 years (range 1-76 years); HBeAg negativity in 132 patients; HBV DNA median log 3.5 log(10) IU/ml (range 2.0-6.0); ALT median level 60.7 IU/l (range 8-874)).

RESULTS

The overall prevalence of typical HBsAg escape mutations found in the CHB patients was 8.3% (27/327). In the NUC therapy group the prevalence was 8.5% (12/142), with the following patterns: sY100C+sI110V, sL109I, sP120T, sP127T, sG130R+sG145X, sS132A+sY134N, sY134N+sG145R, sC137G, sD144E, sG145R. In the treatment-naïve group the prevalence was 8.1% (15/185), with the following patterns: sL109I, sI110V, sS117INST, sP120T, sP127T, sM133I, sC137L+sG145R, sS143L. However, NUC resistance mutations were found in 7.7% (11/142) of the patients on NUC therapy and 3.8% (7/185) of the treatment-naïve group patients. Interestingly, the treatment-naïve patients had preexisting drug resistance mutations related to lamivudine (rtL180M+rtM204I), adefovir (rtA181V, rtQ215S, rtI233V), entecavir (intermediate susceptibility with rtL180M+rtM204IHBV variant), telbivudine (rtL180M+rtM204I), and tenofovir (rtA194T).

CONCLUSIONS

The findings of this study show preexisting typical HBsAg escape and NUC resistance mutations are possible. The genetic arrangement of the HBV genome with polymerase and surface genes overlapping has substantial public health and diagnostic implications and relevance.

Geographical and genetic diversity of the human hepatitis B virus

Hepatitis B virus (HBV) is one of the most widely distributed viruses that infect humankind. Distinct clinical and virological characteristics of the HBV-infection have been reported in different geographical parts of the world and are increasingly associated with genetic diversity of the infecting virus. HBV is classified into genotypes and subgenotypes that are associated with ethnicity and geography. The genetic diversity of HBV in its various aspects has been the subject of extensive investigations during the last few decades. Since molecular epidemiology research tools have become widely available, the number of new publications in this field has grown exponentially. This review summarises the recent publications on the geographical distribution of genetic variants of HBV, and proposes updated criteria for the identification of new genotypes and subgenotypes of the virus.

Naturally occurring amino-acid substitutions to nucleos(t)ide analogues in treatment naive Turkish patients with chronic hepatitis B

Naturally occurring amino-acid substitutions in the hepatitis B virus (HBV) polymerase gene may be responsible for resistance to nucleoside/nucleotide (NUCs) analogues. To date, only pre-existing lamivudine resistance has been extensively studied. The aim of the present study was to determine the naturally occurring or pre-existing amino-acid substitutions related to NUCs in treatment naive Turkish patients with chronic hepatitis B (CHB). The investigation involved a total of 88 patients (65 males and 23 females; mean age, 34 years; range, 15-61 years) who were diagnosed with CHB between April 2008 and January 2009. According to HBeAg status, 66 patients were HBeAg-negative and 22 patients were HBeAg positive. Naturally occurring substitutions in the HBV polymerase region were detected by DNA sequencing in 17 (19%) and 30 (34%) patients, based on manual and geno2pheno tool database interpretation, respectively. Each amino-acid substitution appeared alone and included rtA194T, rtV214A, rtQ215S, rtI233V and rtN236T. The median values for viral load, ALT and AST were 3.3 log(10) (2.0-6.0) IU/mL, 36 (12-515) U/L and 27 (13-284) U/L, respectively, but these did not correlate with the observed amino-acid substitutions in the polymerase region. By direct sequencing, genotype D of HBV was found to still be dominant among Turkish patients. In conclusion, every patient who is diagnosed with CHB should be monitored before the start of treatment for more effective management of patient treatment options.

Hepatitis B virus: the genotype E puzzle

Hepatitis B virus (HBV) is highly endemic throughout sub-Saharan Africa. One of the two genotypes A and E dominates in most countries. With several subgenotypes and variants, genotype A is more diverse in Africa (4.00%) than in the rest of the world (2.96%), suggesting an African origin and a long history on the continent. Despite the African slave trade, genotype E has only sporadically been found within the Americas, indicating that this genotype was introduced only during the past 200 years into the general African population. A short history for this genotype in Africa is also supported by its conspicuously low genetic diversity (1.75%), which contrasts, however, with its excessively high HBsAg prevalence and its extensive spread throughout the vast West-African genotype E crescent. We discuss the spread and routes of transmission of genotype E and suggest that the distribution and current high prevalence levels of HBV (genotype E) in Africa are the result of the extensive use of unsafe needles, potentially solving the current African genotype E puzzle and shedding new light on the high HBV prevalence in Africa.

Efficacy of hepatitis B virus (HBV) DNA screening and characterization of acute and occult HBV infections among blood donors from Madrid, Spain

BACKGROUND

Screening of blood units for hepatitis B virus (HBV) DNA identifies donations collected during the window period (WP) of the acute infection and may improve viral safety of the blood supply. It also leads to the detection of occult hepatitis B infection (OBI).

STUDY DESIGN AND METHODS

From January 2005 to December 2006, a total of 383,267 blood units were screened for hepatitis B surface antigen (HBsAg) and HBV DNA in two transfusion centers in Madrid, using either individual-donation nucleic acid testing (ID-NAT) or minipool (MP-NAT) of eight donations (MP8). Samples positive for HBV DNA and negative for HBsAg were confirmed by a second molecular test, the viral DNA was quantified, and a genome fragment including the region encoding the major hydrophilic region (MHR) of HBsAg was sequenced.

RESULTS

The overall yield of HBV DNA-positive, HBsAg-negative units was 1 in 21,282 (18 cases), higher when using ID-NAT than MP8-NAT (1:9862 vs. 1:51,011; p < 0.01). Four donations (1/95,817) were collected during the infectious pre-HBsAg WP, one during an early recovery stage, and the remaining 13 (1/29,482) were OBIs, six of whom had no detectable antibody to HBsAg. Low-level Genotype D HBV DNA was detected in all OBI cases; the frequencies of this genotype and MHR amino acid substitutions were significantly higher than reported from unselected Spanish HBsAg carriers. Donors with OBI had normal aminotransferase levels and were significantly older than donors carrying HBsAg.

CONCLUSIONS

Blood donors in the WP and with OBI are not uncommon in Madrid and are detected at a higher frequency with ID-NAT than MP-NAT.

Characterization of occult hepatitis B virus from blood donors carrying genotype A2 or genotype D strains

BACKGROUND/AIMS

Nucleic acid testing (NAT) for hepatitis B virus (HBV) DNA in blood donations identified occult HBV infection (OBI) as a potential threat to blood safety.

METHODS

A collaborative study was undertaken to explore the molecular basis of OBIs prevalent in Europe in relation to clinical and serological data.

RESULTS

Ninety-one percent of 77 donor samples of European origin HBV DNA positive but HBV surface antigen (HBsAg) negative were confirmed. Viral load ranged between unquantifiable and 5640 IU/mL (median 25 IU/mL). Fifty-two strains were genotyped (14 HBV(A2) and 38 HBV(D)). Compared to HBsAg+ samples, genotype D was significantly more frequent than genotype A2 in OBIs from Poland or Italy (P<0.04). Amino acid substitutions were concentrated in the immunologically active parts of the Pre-S/S proteins (P<0.0001) affecting both cellular CD8 T-cell epitopes and B-cell neutralizing Major Hydrophilic Region epitopes. Substitutions were more frequent in OBIs than in HBsAg+ strains of both genotype D (P<0.001) and A2 (P<0.01), in OBIs of genotype D than A2 in the 'a' region (P<0.001) but not cellular epitopes, and in anti-HBs+ than anti-HBs- OBIs (P<0.001).

CONCLUSIONS

Results support the hypothesis that humoral and cellular immune pressure on the HBV envelope proteins are major mechanisms generating OBI.

Improved detection of natural hepatitis B virus surface antigen (HBsAg) mutants by a new version of the VITROS HBsAg assay

The sensitivity of immunoassays for hepatitis B virus (HBV) surface antigen (HBsAg) detection may be hampered by the presence of mutants involving the major antigenic determinant of the protein. The performance of the VITROS HBsAg Assay has been shown to be affected by mutations comprising amino acid changes at residues 143, 144, and 145 of the HBsAg molecule. Sixty-seven serum samples from HBV carriers containing major populations of natural HBsAg mutants assayed previously by that assay were tested by the new VITROS HBsAg ES Assay. Samples displayed either single or multiple amino acid substitutions between positions 112 and 145 of the HBsAg, including changes in relevant residues such as 118-120, 125-127, and 143-145. Testing of undiluted samples by the current assay gave rise to false negative results in two samples displaying the single substitutions 145A and 145R, and in one additional sample displaying a dual mutation 118A + 145A. Unusually weak reactivity (<25 S/CO units) was, in addition, recorded in samples containing mutants 143L (2 samples) and 115N + 120Q + 131K + 144A (1 sample). Testing samples at the 1/40 dilution by the modified assay did not produce, in contrast, false negative results, and reactivity below 25 S/CO units was recorded only in three cases. These results confirm that the capability of immunoassays to detect the presence of natural HBsAg mutants in clinical samples may be improved significantly by introducing changes in their design, and show that such improvement has been achieved successfully with the new VITROS HBsAg ES Assay.

Viral and Clinical Factors associated with Surface Gene Variants among Hepatitis B Virus Carriers

Background

Understanding the prevalence of potential antigenic variation of the hepatitis B virus (HBV) surface antigen (HBsAg) is fundamental for assay design and to future changes in vaccine formulation. In this study, the nature and frequency of HBsAg polymorphisms occurring in France in chronic carriers and in newly diagnosed patients were determined. We focused on variations in the major hydrophilic region (MHR), the central core of HBsAg known to be exposed on the surface and involved in antibody binding.

Methods

Two patient groups were identified: 51 chronic HBV carriers followed at our institution for >1 year; and 129 newly diagnosed patients (63 of whom had a first HBsAg-positive result at our hospital laboratory and 66 a first positive result in a private laboratory). DNA sequences of HBsAg were obtained from these 180 patients and compared with consensus sequences built with 168 full-length HBV sequences imported from GenBank. Polymorphisms of the MHR of HBsAg were analysed with the Mutation Master Software. Literature review and BLOSUM scores were used to define potentially altered antigenicity.

Results

The global frequency of MHR variants was 27.8%. Occurrence of MHR variants was independent of viral load, HBeAg status and sex, but was associated with the chronic carriers’ group, advancing age, the presence of antibodies to HBsAg, immunoprophylaxis administration, antiviral treatment and genotypic resistance to antivirals. In multivariate analysis, the independent variables associated with MHR variants were advancing age and the presence of genotypic resistance to nucleoside or nucleotide analogues.

Conclusion

Most MHR variants emerge with longer disease duration and upon indirect selective pressure. Variation of the MHR may serve to restore virus replication of resistant strains. Combined envelope and polymerase variants could impair diagnostic assays and limit treatment alternatives.

Multicenter study of a new fully automated HBsAg screening assay with enhanced sensitivity for the detection of HBV mutants

In a multicenter study a new, fully automated Roche Diagnostics Elecsys HBsAg II screening assay with improved sensitivity to HBsAg mutant detection was compared to well-established HBsAg tests: AxSYM HBsAg V2 (Abbott), Architect HBsAg (Abbott), Advia Centaur HBsAg (Bayer) Enzygnost HBsAg 5.0 (Dade-Behring), and Vitros Eci HBsAg (Ortho). A total of 16 seroconversion panels, samples of 60 HBsAg native mutants, and 31 HBsAg recombinant mutants, dilution series of NIBSC and PEI standards, 156 HBV positive samples comprising genotypes A to G, 686 preselected HBsAg positive samples from different stages of infection, 3,593 samples from daily routine, and 6,360 unselected blood donations were tested to evaluate the analytical and clinical sensitivity, the detection of mutants, and the specificity of the new assay. Elecsys HBsAg II showed a statistically significant better sensitivity in seroconversion panels to the compared tests. Fifty-seven out of 60 native mutants and all recombinant mutants were found positive. Among 156 HBV samples with different genotypes and 696 preselected HBsAg positive samples Elecsys HBsAg II achieved a sensitivity of 100%. The lower detection limit for NIBSC standard was calculated to be 0.025 IU/ml and for the PEI standards ad and ay it was <0.001 and <0.005 U/ml, respectively. Within 2,724 daily routine specimens and 6.360 unselected blood donations Elecsys HBsAg II showed a specificity of 99.97 and 99.88%, respectively. In conclusion the new Elecsys HBsAg II shows a high sensitivity for the detection of all stages of HBV infection and HBsAg mutants paired together with a high specificity in blood donors, daily routine samples, and potentially interfering sera.

Prevalence of hepatitis B, C, and delta virus infections among children in Mongolia: progress in childhood immunization

Mongolia is highly endemic for hepatitis B virus (HBV), hepatitis C virus (HCV), and hepatitis delta virus (HDV) infections among apparently healthy adults. However, the age-specific prevalence of ongoing HBV, HCV, and HDV infections among children in Mongolia remains unknown. Therefore, samples obtained from a total of 655 apparently healthy children of 0.3-15 years of age (307 boys and 348 girls; age, mean +/- standard deviation [SD], 8.4 +/- 4.2 years) living in Mongolia, between October 2005 and January 2006, were tested for serological and molecular markers of HBV, HCV, and HDV infections. Although 88.7% of the 655 children studied were immunized against hepatitis B, 64 (9.8%) tested positive for hepatitis B surface antigen (HBsAg) and/or HBV DNA and 13 (2.0%) for HDV RNA. Twenty-seven children (4.1%) had detectable HCV RNA. Collectively, 82 (12.5%) were viremic for one or more of these viruses, including eight children with dual viremia of HBV/HCV and one child with triple HBV/HCV/HDV viremia. When children without anti-HBc, anti-HCV and anti-HDV IgG (n = 510) served as a control, a history of hospitalization was significantly associated with HBV viremia (P < 0.0001), anti-HBc positivity (P < 0.0001), and HCV viremia (P = 0.0001). HBsAg mutation was found in 18 (31.6%) of the 57 children with viremia, including those at amino acid position 126, 127, 129, 131, 134, 143 or 144. There were no significant differences in the frequency of HBsAg mutation in relation to age, sex, and hepatitis B vaccination status of the children, suggesting that HBsAg mutation plays a limited role in failure of vaccination in Mongolia.

Early upsurge in anti-HBs titer possibly caused by the immunomodulative, not by the mutagenetic effect of interferon and ribavirin

A patient with chronic hepatitis B and C undergoing treatment with interferon and ribavirin showed an upsurge in hepatitis B virus surface antibody (anti-HBs) titer, accompanied by a decrease in hepatitis B virus surface antigen (HBsAg) during the early treatment phase. Simultaneously, elevation of alanine aminotransferase (ALT) was observed. Subsequently, the hepatitis B virus (HBV) DNA titer decreased and HBV e antigen (HBeAg) to anti-HBe seroconversion occurred. The anti-HBs titer gradually returned to the pretreatment level after cessation of ribavirin treatment and HBV-DNA became undetectable. We found no nucleotide mutations in HBV-DNA that could explain the sudden elevation in anti-HBs titer. The appearance of anti-HBs was considered to be a break in immune tolerance against some epitopes in HBsAg, possibly the r epitope, stimulated by interferon/ribavirin treatment. The immunomodulatory effect of ribavirin might have caused this unexpected early immune response to HBsAg that preceded seroconversion to anti-HBe.

A new hepatitis B virus vaccine escape mutation in a renal transplant recipient

Surface antigen mutations of hepatitis B virus (HBV) may lead to immune escape and cause failure of immunization. In this report, the development of a chronic HBV infection in a vaccinated renal transplant recipient with pre-existing anti-HBs antibody is documented. The sequencing data showed that the HBV strain carried five amino acid substitutions in the major hydrophilic region of the S protein, one (sS143L) located at the "a" determinant. A commercial HBsAg assay failed to detect the mutant antigen.

Detection of HBsAg mutants in a population with a low prevalence of hepatitis B virus infection

Two independent studies were conducted to evaluate performance of two HBsAg immunoassay products performed on the Abbott ARCHITECT and Bayer ADVIA Centaur immunoassay analyzers. One was a retrospective study of 484 stored samples and the second was a prospective study of 349 samples from random population. In the process of the evaluation, a number of discordant samples from HBsAg-positive patients were found which led to the discovery of a number of HBsAg mutants in the general Australian population. Following viral DNA sequencing, these were identified as HBsAg escape mutants. Whilst the existence of HBsAg mutants has been well documented in various regions of the world, this is surprising in an area of low endemicity and demonstrates the necessity of an HBsAg assay to detect mutants reliably in a diagnostic situation where HBsAg is used as the only marker to detect an HBV infection. These studies demonstrate the ability of the Abbott ARCHITECT and AxSYM HBsAg immunoassays to detect these HBsAg mutations which were not detected by the Bayer ADVIA Centaur.

Analysis of hepatitis B surface antigen mutations in Mongolia: molecular epidemiology and implications for mass vaccination

Although the potential significance of hepatitis B surface antigen (HBsAg) mutants for failure of immunization has been studied in some endemic countries, whether the "a" determinant variants are responsible for vaccine failure in Mongolia remains unknown. Fifty-nine HBsAg-positive children (age: 8.8 +/- 0.9 years) who had been observed during the nationwide survey of vaccinated cohorts conducted in 2004 were subjected to molecular analyses of hepatitis B virus (HBV). Partial S gene sequences encoding amino acids (aa) 40-171 of HBsAg were determined in 57 children (96.6%) who had detectable HBV DNA. Phylogenetic analysis of the S gene sequences revealed that genotype D accounted for 93.0% and genotype A for 5.3%. Only one child (1.7%) had HBVs of genotypes A and D. HBsAg mutations were found in 17 (29.8%) children ranging from 1 to 4 aa per subject (mean +/- SD, 1.6 +/- 0.9 aa). Pro127Thr and Thr118Ala were the most common substitutions, which occurred in 6 (10.5%) and 3 (5.3%) subjects, respectively; none had Gly145Arg. There were no significant associations in the prevalence of HBsAg mutations with age, sex, residential area, or vaccination status against hepatitis B. Analysis of the deduced amino acid sequence of the entire preS1/preS2/S gene revealed that eight genotype D isolates and one genotype A isolate were quite similar to previously-reported wild-type isolates, suggesting that they are essentially wild-type, but not vaccine-induced mutants. In conclusion, the results demonstrate that hepatitis B surface gene mutants do not play a significant role in vaccination failure in Mongolia.

[Microbiological diagnosis of viral hepatitis]

Hepatitis of viral aetiology caused by hepatotropic virus (A, E, B, D and C) represents an important work load for the clinical virology laboratory. Most of the diagnostic is based upon detection in serum and plasma samples of different serological and virological markers, which correlates with different infection stages. In chronic infection by HBV and HCV is necessary to perform diagnostic by molecular methods as well as antigen detection in sequential samples along the course of the disease taking into account that a reliable storage must be provided for stability of structural components of the virus. Recent knowledge about mutations variants in some of the virus may alter the validity of particular markers.

Hepatitis B virus genetic diversity

Hepatitis B virus (HBV) is a human DNA virus, which replicates through an RNA intermediate because of the reverse-transcriptase (RT) activity of its DNA polymerase. As a result, the mutation rate for HBV is higher than the rate observed for most DNA viruses. HBVs are classified into genotypes based on genomic sequencing, and antigenic subtypes based on the antigenic properties of its major surface glycoprotein, the HBV surface antigen (HBsAg). Subgenotypes have been identified within most of the HBV genotypes. The HBV groups defined by the different genotype-HBsAg subtype associations found over the world display characteristic geographical distributions, reflecting the movements of human populations and other epidemiologically significant events. Such HBV groups constitute genetically stable viral populations sharing a common evolutionary history, but additional stable changes, originating from mutation and mutant selection, are observed within all of them. These viral sub-populations are known as the HBV variants, and some of which have medical and public health relevance. Pre-core (pre-C) defective variants have been shown to make HBV infection much less susceptible to interferon treatment, and treatment failures with other antiviral drugs have been associated with selection of resistant variants that display specific mutations in the genome region encoding the viral RT activity. Since the RT region of the genome overlaps the sequence encoding the HBsAg molecule, selection of drug resistant variants involves, in some cases, the indirect selection of HBsAg variants. Viral variants displaying changes in HBsAg seem to be very common among chronic HBV carriers; and some of these variants may emerge under the pressure of the neutralizing antibody response, leading to vaccine resistance and resistance to immunotherapy. Mutations conferring resistance to immunotherapy are noted often among liver transplant recipients and among babies born to HBV-carrier mothers. In addition, some of these HBsAg variants have been associated with lack of detection by HBsAg tests used for the diagnosis of HBV infection, for the identification of chronic carriers, for screening of blood donations for transfusion, and in the manufacture of therapeutic blood products.